Clamping of parts by adherence on axial thrust support

ABSTRACT

A clamping device, especially for pistons of internal combustion motors, permitting previous indexing and ensuring the handling and maintenance in position of the said pistons during the halffinish and finish machining operations of the skirt and the lands of said pistons. The device comprises a receiving member in frontal support of the head of a workpiece, presenting, centering and indexing members for the piece towards the said receiving member, and members intended to apply the piece against the presenting member by supporting the face of the head of the piece opposite to its face which is frontally supported against the receiving member.

United States Patent Lecailtel et al.

14 1 Aug. 26, 1975 CLAMPING ()F PARTS BY ADHERENCE ON AXIAL THRUST SUPPORT [75] Inventors: Pierre Lecailtel; Bruno Dressler,

both of Billancourt, France [731 Assignees: Regie Nationale des Usincs Renault,

Billancourt; Automobiles Peugeot, Paris, both of France.

[22] Filed: Aug. 22, 1973 [2|] Appl. No.: 390,534

Related US. Application Data [62] Division of Ser. No. 204,151, Dec. 2, 1971, Pat. No.

[30] Foreign Application Priority Data Dec. 4, i970 France 70.43694 Nov. 24, 1971 France 71.42070 [52] US. Cl 279/1 L; 279/5; 269/50; 269/52, 82/40; [51 1 Int. Cl. B23B 5/24; 8238 33/00 [58] Field of Search 279/5, 1 J, 16, l L, l R; 82/40;45 269/50, 52

[56] References Cited UNITED STATES PATENTS 1.794.424 3/1931 Smith et al 82/40 X 2.558005 6/1951 Sciaky 269/52 X 2995,9119 8/196] Lcboime 1 269/52 X 3,200,711 8/1965 Rogg 1 1 269/50 X 3,460,239 8/1969 Nix 269/52 X Primary Examiner-Leonidas Vlachos Attorney, Agent, or FirmStevens, Davis, Miller & Mosher [57] ABSTRACT A clamping device, especially for pistons of internal combustion motors, permitting previous indexing and ensuring the handling and maintenance in position of the said pistons during the half-finish and finish machining operations of the skirt and the lands of said pistons.

8 Claims, 5 Drawing Figures 5 V/IIIAV/ & r78

PATENTED AUG 2 8 I975 SEiZET 3 BF 3 CLAMPING OF PARTS BY ADHERENCE ON AXIAL THRUST SUPPORT This is a division of application Ser. No. 204,151, filed Dec. 2, l97l, now US. Pat. No. 3,795,405.

The present invention relates to a clamping device permitting previous indexing and ensuring the clamping and maintenance in position of engine pistons during semi-finish and finish machining operations of the skirts and the lands.

These machining operations give their final form to the profile of the generator line and the rectangular sections of the pistons. Until the last few years, only the machining of the skirt of the piston was required to comply with severe tolerances necessitating the use of a copying machine. During this machining, the gripping of the part was effected by a claw chuck gripping the first land of the head.

There is now a tendency to make the lands help in the guiding of the pistons and to require from them new qualities. These lands must in particular have a complex rectangular section, at the same time being perfectly concentric to the skirt. In consequence, it is now not only the skirt of the pistons which must be machined on a copying machine, but the whole of the generator line profile of the piston.

A machining operation of this kind is effected according to the invention by means of a new clamping device for the work-pieces. This device has the following advantages:

It leaves the whole generator line of the piece free for machining, gives good trueing and good centering of the piece and causes minimum deformation due to clamping while permitting previous automatic indexing.

Up to the present time, efforts have been made to obtain such a result by effecting clamping of the piece by means of a claw chuck, using a boss machined on the compression face of the piston.

This solution provides good trueing and good centering of the piece without deformation of the holding means of the piece, but it is expensive since it requires additional operations, firstly for the machining and then for removing the boss. lt becomes very expensive when the compression face of the piston is required to be machined.

The clamping device for pistons forming the object of the invention comprises essentially a receiving member frontally supporting the head of the piece, members for presenting, centering and indexing the piece towards the reception member, and devices intended to apply the piece against the presenting member by pressing against the face of the head of the piece opposite to its frontal support face on the reception memher.

According to a particular form of embodimentvof the invention, the reception member is a circular plate carrying three supports cut so as to present, each, four truncated pyramid points. These three supports are provided in the vicinity of the periphery of the plate and are angularly spaced apart by 120. The plate, which also comprises three retractable contact fingers serving to support the piston during indexing, is surrounded by a retractable ring.

The presentation and indexing members comprise essentially an oscillating thrust rod free for rotation about its own axis, elastically coupled to a thrust body,

and two indexing fingers rigidly fixed to the thrust body and intended to serve as an angular abutment for the bosses of the axis holes of the piston during indexing.

The thrust rod which has especially the purpose of forcing the piston against the plate, is coupled to the for clamping.

By virtue of this clamping device, the skirt of the piston is entirely free for machining. During semi-finish machining, the applied supporting force is about three times greater than in the case of finishmachining.

In this device, the head of the workpiece, for example the upper face of a piston, is applied against a reception member complete with centering and indexing members for the piece towards the said centering member, thrust members, in the present case a central supporting finger, applying the piece, by pressure on the face opposite to the head-face, against the receiving member. I

In the case of pistons, this arrangement has the advantage on the one hand of completely freeing the outer cylindrical face, which enables it to be machined without repeating the operation, and on the other hand it limits the supporting and clamping points to the face of the piston head in the absence of any direct mechanical stress on the skirt, which reduces the risk of deformation due to clamping.

However, since technical development is leading to lighter and lighter pistons and therefore to smaller thicknesses of diaphragm plates on the head-faceand the skirt it appeared that non-coincidence of the supports on each side of the head face could result in certain casesin elastic clamping deformations on the skirt. Furthermore, the precision of centering by rings is conditioned by the accuracy of the diameter of the rough piston and their adjustment. 1

The present invention provides a solution for these problems while at the same time it simplifies the previous form of construction.

The clamping device according to the invention is characterized by the fact that the receiving member is a circular plate carrying a number of supports placed in the vicinity of the periphery of the plate, the presenting members comprising a thrust rod carrying a rocking lever mounted with a swivel joint on the extremity of the thrust rod, the said rocking lever comprising a number of points which cooperate on the internal face of the piston head with the said supports of the circular plate. 1

According to a preferred form of construction of this device, the clamping is modified as follows:

Centering: this is effected by three retractable elastic fingers moving in synchronism along the generator lines of acone;

Clamping by internal thrust: the thrust is applied at three points level with the supports of the plate, through the intermediary of three toes mounted on a rocking lever articulated by a swivel joint on the extremity of the thrust rod. There is therefore no deformation of the piston as a result of its clamping, due to the fact of the coincidence of the points of support on each side of the diaphragm plate;

Indexing: The piston is installed pre-indcxed. Fine indexing is effected by a member comprising V-shaped portions which is supported on the bosses of the shaft hole and angularly positions the piston with precision. This indexing is effected during the forward movement of the thrust rod;

Clamping force: The previous. modifications render superfluous the necessity of creating two different conditions of force for the indexing and finish machining on the one hand, and for the rough machining on the other.

The present invention will now be illustrated by means of the description which follows of a particular device given with reference to the accompanying drawings, in which:

FIG. 1 represents a general view of the device in cross-section;

FIG. 2 represents to a larger scale the control portion of the device between the line AB of FIG. 1;

FIG. 3 represents a'view from above of a support of the piston-carrier plate;

FIG. 4 shows a view of the support shown in FIG. 3, in cross-section taken along line IVIV;

FIG. 5 represents another form of construction of the device, seen in cross-section.

The device according to the invention comprises a piston-carrier plate 1 equipped with three supports 2 spaced apart by 120 and each constituted by four truncated pyramid toes.

Also at the periphery of the plate 1 and'at 120 from each other are placed three contact fingers 3 against which is applied the compression face of the piston at the moment ofits indexing.

The plate 1 is enclosed by a retractable centering ring 4. The forward and reverse movement of this ring are controlled by a member 5. A spring 6 urges the ring 4 in reverse, while a jack 7 causesits forward movement. A spring 8 acting on the ring 4 adds its action to that of the three elastic fingers 3 and of the piston ejector 9. The result is that the piston is only in contact with the fingers 3 during the indexing; as the ring 4 is withdrawn during machining, the support is effected at 2.

A thrust rod 11 is mounted on a ball abutment and is for that reason free to rotate. Two indexing fingers l2 and 12' are intended to be supported against the bosses of the shaft holes of the pistons. A spring 13, provided for indexing and finish machining, is rigidly fixed to the slide 15. A spring 14, provided for semifinish machining, is supported against the circular plate 16 which abuts against the shoulder 21 .of the thrust body. The forward or reverse movement of the thrust body 17 is controlled by the oppositely-acting jacks 18 and 19.

OPERATION OF THE DEVICE 1. State of the device before presenting a piston l-l. Spindle side The fingers 3 are pushed into abutment by their spring; The ejector 9 pushed by its spring 10, is in abutment; The ring 4 is moved forward by the jack 7, through the intermediary of the spring 8. l-2. Clamping device side The jack 18 being under pressure, its piston rod is in forward abutment: The assembly 17 is at the end of its rear travel. by

means of the jack 19;

The cone located to the rear of the rod 11 is in contact with the washer'l6.

2. State of the device necessary for indexing (Case of 5 FIGS. 1 and 2) 2-1. Spindle side The fingers 3 are still in abutment, pushed by their spring;

The piston P, subjected to the action of the clamping device. is supported on these fingers 3 and pushes back the ring 4 together with the ejector 9.

2-2. Clamping device side The jack 18 is still under pressure;

The jack 19 has moved the device 17 forward and therefore the piston; the jack 18 is under pressure and serves as an abutment;

In this case, the rod 11 acts on the piston P; the cone located at its rear extremity is no longer in contact with the washer 16;

The slide 15 coupled axially to the rod is not in contact with 16 and is only subjected to the action of the spring 13.

3. Indexing The spindle is set in rotation at low speed; it drives by adherence the piston P, which is stopped angularly against the fingers 12 and 12. The spindle is indexed in turn.

The piston P and thespindle having been separately indexed with respect to the frame of the machine are thus in consequence indexed with respect to each other.

The reverse movement of the sheath 22 ensures the withdrawal of the fingers l2 and l2.

4-1. Spindle side The ring 4 is withdrawn by means of the jack 7 and the spring 6;

The piston P is supported at 2 and offers its lateral surface completely;

The fingers 3 and the ejector 9 are pushed back by the piston P.

4-2. Clamping device side The jack 18 having been put off-pressure, its piston has returned under the thrust of the jack 19;

The device 17 thus moves forward by a few millimeters and the washer 16 comes into contact with the slide 15; the spring 14 thus applies the necessary clamping force for semi-finish machining.

5. State of the device necessary for finish machining.

6. Ejection of the piston 6-]. Spindle side condition The fingers 3 and the ejector 9 are pushed into abutment by their spring. The ejector 9 ensures the moving away of the piston;

The ring 4 remains withdrawn.

6-2. Clamping device side condition The jack 19 remains under pressure; The jack 19 has moved back the device 17. As can be seen from-FIG. 5, the reception members for the piston P to be clamped comprises a rod 51 which is in co-operation with a jack (not shown) and is surrounded by a slide member 52 associated with a spring 53. The receiving member also comprises three centering fingers 54 guided by a conical internal surface of ainandrel 55, and a face-plate 67 provided with three supporting members for the top face of the head of the piston P. The movement of the centering fingers'5 4 is synchronized by the slide member 52. l v i Y lnside piston P are fitted two members 56 and 57, one a rockable support member 56 and the other an aligning ring 57 for effecting rotary alignment of the piston. These members are mounted on a thrust rod 58 which is slidable in and articulated by a swivel bearing 59. The push-rod 58, actuated by a jack (not shown), is fixed against rotation when transverse pegs 79 engage recesses 78 but is otherwise free for rotation in a thrust body constituted by the assembly of parts 60. The aligning ring 57 has V-shaped recesses which cooperate with bosses 61 of gudgeon pin holes of the piston P. This piece 57 is also movable longitudinally relative to the thrust rod 58 through the intermediary of two spring-loaded balls 62 which are situated in grooves on the rod 58 which carries at its extremity the rockable support member 56 having three pegs 63 for supporting the underside of the head of the piston P. The recesses 68 of the two grooves of the thrust rod 58 serve to lightly restrain the ring 57 against axial move ment of the thrust rod 58 when the balls 62 engage the recesses 68.

A spring 64, mounted on the end portion of the thrust rod, 58 provides the clamping force and is supported for reaction against an abutment 66 which receives the swivel-joint bearing 59 in the thrust body 60. A spring 65 urges the rod 51, the slide member 52 and the centering fingers 54 in a direction away from the face plate 67.

The operation of the device is as follows:

The rod 51 is moved forward by a jack (not shown) and frees the slide'member 52 which is pushed to the right, as seen in FIG. 5, by the spring 53 taking with it the centering fingers 54 guided by the mandrel 55.

The piston P, fitted on the aligning ring 57 and the rockable support member 56 is then moved towards the centering fingers 54 by the thrust rod 58. The thrust rod 58 is actuated by a jack, not shown, through the assembly of parts 60. The bosses of the gudgeon pin holes 61 of the piston are housed in the Vshaped recesses of the ring 57. The rotary alignment is then carried out by the pressure of the V-shaped recesses on the bosses 61- at the moment when the piston head passes into the centering fingers 54 and is centered inside the said fingers. During the alignment process, the transverse pegs 79 engage the recesses 78 under the influence of the spring 64, and the thrust rod 58 and the aligning ring 57 and thus fixed against rotation.

The centering and angular aligning are therefore simultaneous. Under the effect ofthe pressure applied by the thrust rod 58, the two balls 62 rise out of their respective recesses 68 and the thrust rod 58 carrying the rockable support member 56 is applied by its three pegs 63 against the underside of the head of the piston. Further movement of the thrust body towards the receiving member causes the spring 64 to be compressed, and the transverse pegs 79 are disengaged from the recesses 78 and the thrust rod 58, aligning ring The centering fingers 54 are retracted by reversing the jack actuating the rod 51. The spring 65 then pushes back the rod 51, the slide member 52 and in consequence the fingers 54.

All the skirt and land region of the piston P is then free for machining. The head of the piston P is fixed solely between the three supporting members of the plate 67 and the three corresponding directly oppositely located supporting pegs 63 of the rockable support element 56 and is thus not subjected to any clamping distortion.

What is claimed is: l. A clamping device for pieces to be machined adapted for the initial centering and indexing of the work piece such as a piston comprising:

a receiving member adapted for frontly supporting a face on the head of a work piece to be machined;

fixed support members positioned on said receiving member for supporting a work piece to be machined;

a retractable centering element surrounding said receiving member for initially centering a work piece to be machined and adapted to be retracted away from the work piece during the machining operation;

an oscillatable: thrust rod free for rotation about its own axis and elastically coupled to a thrust body;

said thrust rod supporting the portion of a work piece to be machined opposite to its face supported by said receiving member;

said receiving member comprises circular plate which carries the fixed support members which are placed adjacent the periphery of said plate; and

a rockable support member articulated by a swivel joint on one extremity of the thrust-rod, the rockable support member having a plurality of supporting points which, when the device is clamping a work piece to be machined, cooperate with the fixed support members on the circular plate.

2. A clamping device as set forth in claim 1, wherein the centering element comprises three centering fingers which are retractable in unison and are guided along generator lines of a cone.

3. A clamping device as set forth in claim 1, wherein there are three fixed support members, and the supporting points of the articulated rockable support member are three pegs angularly spaced apart by which cooperate with the three support members on the circular plate.

4. A clamping device as set forth in claim 1, further comprising:

an alignment member comprising a ring axially slidable on the thrust rod and non-rotatable relative thereto, the ring having V-shaped recesses adapted to engage bosses on a work piece to be machined for carrying out rotary alignment of the work piece. 5. A clamping device as set forth in claim 4, wherein the ring is provided with two spring-loaded balls which co-operate with two axially-extending grooves defined in the thrust rod to prevent rotation of the ring on the thrust rod, each groove terminating, at that end of the groove nearest the rockable support member, in a recess, whereby, when the balls are aligned with the recesses, the ring is retained at a predetermined axial position on the thrust rod.

6. A clamping device as set forth in claim 5, further comprising:

an abutment for the ring, whereby, upon retraction of the thrust rod, the ring is held stationary against the abutment so that the recesses move into alignment with the balls.

7. A clamping device as set forth in claim 1, wherein at least one transverse peg projects from the thrust rod and a recess is defined in the thrust body corresponding to the transverse peg, and a spring is arranged to act between the thrust rod and the thrust body to urge the thrust rod into an axial position in which the peg engages the recess thereby to fix the thrust rod against rotation relative to the thrust body.

8. A clamping device as set forth in claim 1, wherein the thrust rod is mounted in the thrust body by means of a bearing whereby the thrust rod is slidable in the thrust body and is pivotable relative thereto. 

1. A clamping device for pieces to be machined adapted for the initial centering and indexing of the work piece such as a piston comprising: a receiving member adapted for frontly supporting a face on the head of a work piece to be machined; fixed support members positioned on said receiving member for supporting a work piece to be machined; a retractable centering element surrounding said receiving member for initially centering a work piece to be machined and adapted to be retracted away from the work piece during the machining operation; an oscillatable thrust rod free for rotation about its own axis and elastically coupled to a thrust body; said thrust rod supporting the portion of a work piece to be machined opposite to its face supported by said receiving member; said receiving member comprises circular plate which carries the fixed support members which are placed adjacent the periphery of said plate; and a rockable support member articulated by a swivel joint on one extremity of the thrust-rod, the rockable support member having a plurality of supporting points which, when the device is clamping a work piece to be machined, cooperate with the fixed support members on the circular plate.
 2. A clamping device as set forth in claim 1, wherein the centering element comprises three centering fingers which are retractable in unison and are guided along generator lines of a cone.
 3. A clamping device as set forth in claim 1, wherein there are three fixed support members, and the supporting points of the articulated rockable support member are three pegs angularly spaced apart by 120* which co-operate with the three support members on the circular plate.
 4. A clamping device as set forth in claim 1, further comprising: an alignment member comprising a ring axially slidable on the thrust rod and non-rotatable relative thereto, the ring having V-shaped recesses adapted to engage bosses on a work piece to be machined for carrying out rotary alignment of the work piece.
 5. A clamping device as set forth in claim 4, wherein the ring is provided with two spring-loaded balls which co-operate with two axially-extending grooves defined in the thrust rod to prevent rotation of the ring on the thrust rod, each groove terminating, at that end of the groove nearest the rockable support member, in a recess, whereby, when the balls are aligned with the recesses, the ring is retained at a predetermined axial position on the thrust rod.
 6. A clamping device as set forth in claim 5, further comprising: an abutment for the ring, whereby, upon retraction of the thrust rod, the ring is held stationary against the abutment so that the recesses move into alignment with the balls.
 7. A clamping device as set forth in claim 1, wherein at least one transverse peg projects from the thrust rod and a recess is defined in the thrust body corresponding to the transverse peg, and a spring is arranged to act between the thrust rod and the thrust body to urge the thrust rod into an axial position in which the peg engages the recess thereby to fix the thrust rod against rotation relative to the thrust body.
 8. A clamping device as set forth in claim 1, wherein the thrust rod is mounted in the thrust body by means of a bearing whereby the thrust rod is slidable in the thrust body and is pivotable relative thereto. 